Joel is comparing two slides showing chromosomes in a sperm cell and a skin cell of a dog. He finds that the sperm cell has 39 chromosomes. How many chromosomes can he expect in theskin cell? 39 chromosomes
78 chromosomes
38 chromosomes

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.